Energy Storage: Powering a Renewable Future?

Energy storage has been around for a long time, predominantly (in the UK at least) in the form of large pumped hydro stations. However, recent developments in battery and flywheel technologies mean energy storage could soon revolutionise the UK’s electricity network, increasing efficiency and lowering carbon emissions.

Such a revolution is vital. Although the UK has increased electricity generation from renewable sources in recent years, it will need to continue to do so to meet its own and Europe’s renewable and emission reduction targets. This shift towards intermittent sources of electricity creates several problems, one of which is how to best harness such sources of electricity to minimise reliance on traditional generation technologies. Although demand side management, smarter grids and interconnection will hold some of the answers, energy storage will also be hugely important. In fact, forecasts indicate that the global industry could be worth between $30bn and $40bn within seven years.

Much of the recent research and development has been focussed on battery and flywheel storage technologies, which seem to have the greatest potential to accelerate the decarbonisation of the UK’s generation mix. Although mainly in the research and development phase in the UK, both are already being deployed in other markets with apparent success. AES have installed a 40 MW battery storage array in Chile, with a total of more than 200 MW of battery storage in the Americas. In County Offaly, Ireland, a fly wheel is being built with a capacity of 20 MW and an efficiency of 85% - 90% (compared to 35% - 40% efficiency for coal and gas generators). Other technologies continue to be developed, including pumped heat and liquid air storage.

The possibilities

Energy storage by battery and flywheel has the potential to help electricity grids to operate more efficiently and cost effectively. One way of achieving this is by allowing energy produced by intermittent technologies to be stored and then used when it is most needed, not just when the sun shines or the wind blows. This could end the absurdity of National Grid (as the UK system operator) paying wind farms to stop generating at times of lower demand by allowing energy to be stored for use during periods of high demand.

Not only will energy storage assets assist the generation of renewable power, they are also able to provide ancillary services to grid operators by way of frequency regulation. Where demand momentarily exceeds generation, causing a drop in system frequency, battery and flywheel storage has the ability to provide a fast discharge of power to reduce frequency and restore system stability. Currently in the UK, frequency response services are predominantly provided by carbon intensive fossil fuel generators which are slower to respond than both batteries (which can respond in less than a second) and flywheels. Being slower to respond, these generators tend to over compensate and ‘overshoot’ the frequency correction requiring activation of other services to counteract this, causing an additional cost to the system.

Other significant uses include reducing exposure to imbalance charges for balancing system participants and, most importantly, reducing the need for load-related investment in electricity networks by National Grid and DNOs (the cost of which will, ultimately, be picked up by consumers).

So, what is holding energy storage back in the UK?

ESOF (the Energy Storage Operators Forum) highlights several issues, including managing systems in the relative absence of directly applicable codes and legislation, a lack of understanding of storage system performance and developing a viable business case.

Given the potential for use on distribution and transmission networks, clarity on the impact of licensing and regulatory requirements and codes is important. For a DNO to maximise the benefit of owning and operating an energy storage asset, it would need to be able to use the asset in electricity trading, capacity and balancing markets during those times when the asset is not required for system services. However, this would likely put it in beach of the strict requirements of its distribution licence, which will restrict participation in such markets.

In addition to the above issues, the cost of storage technologies may yet be too high for wide scale implementation in the UK. However, costs should drop quickly, much like the huge decrease in cost of solar panels that we have seen over recent years. The option to participate in the upcoming capacity mechanism will also help push the economic case for storage.

A home revolution?

In addition to commercial uses, energy storage could soon play an important role in the home. Tesla recently released its Powerwall device and, here in the UK, Moixa also has a residential scale energy storage device on the market. Such devices will permit households to store electricity generated themselves, most likely by rooftop solar panels. This has a number of potential benefits. It should allow households to increase use of generated electricity (e.g. by allowing self generated consumption from solar in the evenings or when the sun isn’t shining) and it can be used as back up power during black outs. This new wave of home energy storage could help increase the use of small-scale distributed generation, minimising the need for high-cost power plants. The impact of such systems is likely to become increasingly magnified as the cost of such devices begins to drop (Tesla is in the process of constructing a $5bn factory to mass produce the Powerwall).

And finally…

Energy storage must begin to play an ever increasingly important role in the UK’s energy mix if we are to have any chance of meeting our renewable and emission reduction targets. It is now vital that DECC carries out a full review on removing all possible obstacles to the deployment of energy storage technologies, including consulting on the required changes to the regulatory regime. This, along with increased investment in innovation, will help energy storage become an increasingly viable option for generators, DNOs and even households.

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